WTC Dust Cloud Not as Deadly as Expected

Action Points

Explain that people involved in rescue and recovery after the World Trade Center attacks are less likely to have died than members of the general population of New York City.

Note that in participants who were in the area at the time -- but not in the rescue/recovery participants -- higher levels of exposure were significantly associated with mortality.

People involved in rescue and recovery after the World Trade Center attacks are less likely to have died than members of the general population of New York City, researchers reported.

People exposed to the fallout because they were in the area – such as residents, students, and passers-by – also appear less likely than expected to die, according to James Cone, MD, of the New York City Department of Health and Mental Hygiene, and colleagues.

Within that latter group, however, high and intermediate exposure to the event was significantly associated with an increased risk of death, Cone and colleagues reported in the Sept. 3 issue of The Lancet.

Although several health outcomes have been shown to be increased in World Trade Center survivors – including new data in the same issue of The Lancet – mortality has not been assessed, the researchers noted.

To help fill the gap, they turned to the WTC Health Registry. Between Sept. 12, 2003 and Nov. 24, 2004, 71,437 people completed interviews for the registry on demographics, exposures incurred during and after the event, and health information.

In an observational cohort analysis, Cone and colleagues looked at deaths from 2003 through 2009 among registry participants who lived in New York City, using the city's vital records and the National Death Index.

All told, the analysis included 13,337 people involved in rescue and recovery and 28,593 residents, workers, school staff and students, and commuters and passers-by who were present during the events.

The researchers compared death rates within the cohort to those that would have been expected based on the general New York City population from 2000 through 2009, as well as examining the relationship between exposure and the risk of death.

They found:

156 deaths among the 13,337 rescue and recovery workers and 634 deaths in the remaining 28,593 members of the cohort.

The standardized mortality ratio for all causes of death was significantly lower than expected for those involved in rescue and recovery: 0.45 (95% CI 0.38 to 0.53).

The same was true for non-rescue/non-recovery participants, at 0.61 (95% CI 0.56 to 0.66).

No standardized mortality ratios were increased significantly for a range of heart diseases or for hematological malignancies.

In non-rescue/non-recovery participants – but not in the other participants -- intermediate and high exposures were significantly associated with mortality, compared with low exposure. The adjusted hazard ratios were 1.22 for intermediate exposure (95% CI 1.01 to 1.48) and 1.56 for high exposure (95% CI 1.15 to 2.12).

Among the non-rescue/non-recovery participants, high exposure was associated with heart disease-related mortality, when compared with low exposure. The adjusted hazard ratio was 2.06 (95% CI 1.10 to 3.86).

The findings are "not surprising," the researchers argued, because most illnesses that are either established or possible results of the 9/11 events have either long latency or long median survival periods.

Two other factors might also play a role, they noted. First is the so-called "healthy worker effect" -- most of the participants were employed, and employed people in general are healthier than the overall population.

Second, people who offer to participate in health studies tend to be healthier than the general population – a "healthy volunteer effect."

One of the valuable aspects of the study is that it "replaces supposition and assertion founded on anecdote with cold, hard, incontrovertible, well presented data," according to James Feeney, MD, of Saint Francis Hospital and Medical Center in Hartford, Conn., and Marc Wallack, MD of the Metropolitan Hospital Center in New York City.

In an accompanying commentary, they argued that one of the goals of terrorism is to spread fear, which can be countered by facts. "Terrorists rely on fear and doubt to incite terror; today, however, scientific method triumphs," they wrote.

The study was supported by the National Institute for Occupational Safety and Health, the Agency for Toxic Substances and Disease Registry, the National Center for Environmental Health, and the New York City Department of Health and Mental Hygiene. The authors said they had no conflicts.

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